Magnesium oxychloride-terrazzo surfaces



United States Patent 3,482,493 MAGNESIUM OXYCHLORIDE-TERRAZZO SURFACES Clark W. Redeker, Newark, and Ralph G. Schlosser, San Jose, Calif., assignors to FMC Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 11, 1967, Ser. No. 629,902 Int. Cl. E01c 7/35; E04f 15/08 US. C]. 94-22 3 Claims ABSTRACT OF THE DISCLOSURE Method of applying a magnesium oxychloride-based, terrazzo deck or floor to obtain a non-skid, textured surface by depositing on a substrate a smooth, trowelled layer of a magnesium oxide-magnesium chloride cementitious mixture containing chips of mineral or synthetic aggregates, partially drying said layer until it begins to set into a rigid mass, dissolving and removing a thin surface coating of the partially dried cementitious mass, thereby exposing said chips and forming a textured surface on said cementitious mass, allowing the cementitious mass to completely dry and applying a clear, waterimpermeable sealer over said surface.

BACKGROUND OF THE INVENTION Field of the invention The invention covers a method for applying a magnesium oxychloride-based terrazzo deck or floor to obtain a textured, non-skid surface.

Description of the prior art Terrazzo decks or floors are presently made using a magnesium oxide-magnesium chloride matrix. In this process a magnesium oxide-magnesium chloride cementitious mixture containing chips of crushed mineral aggregates, e.g. marble chips, limestone chips, etc. are cast, poured, molded or trowelled and allowed to set; magnesium oxychloride is formed on seting. Thereafter, the surface of the dried mass is slowly ground down in order to expose the surfaces of the chips and obtain a highly polished surface. This grinding of both chips and cementitious mass produces a smooth surface in which the mineral chips are ground down to the same level as the cement matrix so that they are clearly visible, and results in the well-known terrazzo type surface.

One of the difficulties in this technique is the long and expensive grinding that is required to expose the mineral chips in the cement matrix to obtain a finished surface. In some cases prolonged grinding is required because many chips, e.g. traprock, are extremely hard. This required grinding step adds considerably to the cost of laying a terrazzo deck or floor having a magnesium oxychloride-based matrix.

As a result there is a need in this art for a method of laying a terrazzo deck or floor containing a magnesium oxychloride-based matrix which obviates the expensive, time consuming, grinding step currently used to finish the surface of the deck or floor.

SUMMARY OF THE INVENTION We have now found a method for applying a magnesium oxychloride-based terrazzo deck or floor without the need for a grinding stage comprising depositing on a surface a smooth, trowelled layer of a magnesium oxidemagnesium chloride cementitious mixture in which are dispersed chips of mineral or synthetic aggregates, partially drying said layer until it begins to set into a rigid mass, contacting the partially dried surface of the rigid mass with an aqueous solution of either MgCl or HCl,

3,482,493 Patented Dec. 9, 1969 the MgCl solution being at least 14 B. (preferably about 22 B.) and the aqueous HCl solution being at least about 5%, removing a thin surface layer of the rigid mass, thereby exposing said chips and forming a textured surface on said rigid mass, fully drying said rigid mass, and coating said rigid mass with a clear, waterimpermeable (preferably acrylic) sealer.

DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS In the pactice of the present invention, a magnesium oxychloride-based cement is prepared by mixing together magnesium oxide and fillers such as limestone, marble dust, sand, silex, asbestos, wood or talc. This mixture of magnesium oxide and fillers is termed a dry mix and can contain from 25 to 50 weight percent MgO and from 50 to weight percent of fillers. The dry mix is then blended with an aqueous solution of magnesium chloride having a concentration of at least 22 B. Enough magnesium chloride solution is used to obtain a smooth, workable, cementitious mass.

To the above cementitious mass is then added chips of either mineral or synthetic aggregates. The size and shape of the chips will, in general, be determined by the desired terrazzo effect, but generally range in size from A; to of an inch. Conventional mineral aggregates which can be used include chips of marble, limestones or calcites, quartzites, dolomites, traprock and numerous mine tailings. Synthetic aggregates that can be used include various slags, crushed glass, as well as magnesium oxychloride shapes such as those set forth in US. Patent 1,368,- 949, issued to Loeffelhardt on Feb. 15, 1921.

The weight percent of the chips which are added to the cementitious .mass may be varied, depending upon the extent of the terrazzo design which is desired in the final surfaces. conventionally, the chips are present, relative to the dry mix, in a Weight ration of from 1:1 to 2: 1. The entire cementitious mass is then thoroughly blended to yield a thick, flowable mixture which can be poured, cast, molded or trowelled into a variety of shapes. In the preferred process the cementitious mass is trowelled over a substrate to form a level floor or deck. The towelling is carried out to yield a plane surface and also to orient the chips in the cementitious matrix.

The resulting chip-bearing magnesium oxide-magnesium chloride matrix is then permitted to dry, in part, until it commences to set into a rigid mass. The degree of rigidity which is desired is generally that which will just support a workman without leaving tracks. When this degree of rigidity has been reached, but before complete drying, the surface of the mix is treated with an aqueous solution of either magnesium chloride or hydrochloric acid. The concentration of the magnesium chloride should be at least 14 B., and solutions of 22 B. are generally prefered because they are readily available. The aqueous hydrochloric acid solution can be any concentration at or above about 5%. High concentrations of HCl are not generally desired because of fuming problems which may be encountered.

Upon application of the solution of magnesium chloride or HCl, the surface of the partially dried matrix is then brushed so that the solution uniformly contacts the surface of the partially dried matrix. During this brushing stage, a portion of the matrix dissolves, softens and disperses in the hydrochloric acid or magnesium chloride solution. This removes a thin surface coating of the partially dried matrix and exposes the chips which are on the surface thereof.

The surface of the partially dried matrix is then washed with water to remove the magnesium chloride or HCl solution and to also remove the dissolved matrix. The dissolved or dispersed matrix forms a guck on the surface and must be carefully Washed off by hosing and brushing. This surface treatment gives the partially dried matrix a textured surface, in which the chips are clearly visible. This textured surface is particularly desired on patio decks and floors because it yields a non-skid surface.

The thus treated mass is then permitted to dry to its full strength, commonly 24 to 48 hours. Thereafter, a clear, water-impermeable, resinous sealer is applied to the surface. The exact composition of the sealer is not critical to the present invention. Its function is merely to keep water from continuously wetting the magnesium oxychloride-based matrix. Sealers which have been found suitable include resins that are internally plasticized such as methacrylate-acrylate ester copolymers, styrenebutadiene copolymers, vinylacrylic copolymers and polymers such as vinylacetate-vinylchloride copolymers. The acrylic resins, when mixed with a solvent and a surfactant have been found particularly suitable. Certain of the Acryloid resins, manufactured by Rohm and Haas, namely Acryloid B-66 (a methacrylate-acrylate ester copolymer wherein the esters are derived from aliphatic alcohols having from one to four carbon atoms) are preferred.

In the above description of the invention the dry mix was first mixed with the Mgcl -solution and the chips subsequently added. However, if desired the dry mix can be blended with the chips first, and this mixture then blended with the MgCl -solution. In this latter case the MgO content of the whole dry mix, including chips, should be kept between 13 and 20 weight percent to give optimum results.

The following examples are given to illustrate the invention and are not intended to limit the scope thereof.

EXAMPLE 1 A terrazzo mixture was made up as follows. A dry mix, as defined below, was blended with enough aqueous 22 B. MgCl solution to yield a readily workable cementitious mixture. The dry mix contained (by weight To the resulting cementitious mixture was added granite chips, having a hardness between granite and traprock (product of Watsonville Granite Co., Watsonville, Calif.) in a weight ratio of chips to dry mix of 1:1. The resulting cementitious mixture, containing the added chips, was then laid out to form a 650 square foot deck, and the surface of the mixture was trowelled fiat. During trowelling the chips in the mix were oriented and exhibited a flat surface on the surface of the deck. The deck was allowed to set until the surface was just hard enough to walk on without leaving marks on the surface. Thereafter, the surface was flooded with 22 B. MgCl and scrubbed with a stiff broom to remove a thin coating of the cement from the surface. Immediately thereafter, the surface was scrubbed lightly with rotating brushes having means for spraying water onto the brush bristles. The water and the brushes removed all loose guck (dissolved surface layer of the cementitious mixture) from the surface of the deck. The excess water was then removed (squeegeed) from the deck by means of a rubber stripped squeegee, and the deck permitted to completely water during the above surface treatment for about 15 minutes. After the deck had set, it was covered With a clear acrylic resin having the following composition:

Parts by weight Rohm and Haas Acryloid B-66 Resin (40% solids) -1 45 (a methacrylate-acrylate ester copolymer wherein the esters are derived from aliphatic alcohols having from one to four carbon atoms) Aromatic solvent 55 Cellulsolve acetate 1.5

The resulting terrazzo deck had a smooth, textured, nonslip surface, and the chips were plainly visible at the surface of the deck.

EXAMPLE 2 The procedure of Example 1 was repeated except that magnesium oxychloride aggregates were used in place of granite chips, and a 5% aqueous HCl solution was employed in place of aqueous MgCl The results obtained were substantially the same as those obtained in Example 1.

Pursuant to the requirements of the patent statutes, the principle of this invention has been explained and exemplified in a manner so that it can be readily practiced by those skilled in the art, such exemplification including what is considered to represent the best embodiment of the invention. However, it should be clearly understood that, within the scope of the appended claims, the inven tion may be practiced by those skilled in the art, and having the benefit of this disclosure otherwise than as specifically described and exemplified herein.

What is claimed is:

1. Method of applying a magnesium oxychloridebased, terrazzo deck comprising depositing on a surface a smooth, trowelled layer of a magnesium oxide-magnesium chloride cementitious mixture containing chips selected from the group consisting of mineral and synthetic aggregates, partially drying said layer until it begins to set into a rigid mass, flooding the partially dried surface of said rigid mass with an aqueous solution of a compound selected from the group consisting of magnesium chloride and hydrochloric acid, to dissolve, soften and disperse the surface layer of said cementitious mixture, removing a surface layer of said rigid mass with said aqueous solution of sufficient thickness to expose said chips and form a textured surface on said rigid mass, fully' drying said rigid mass, and coating said rigid mass with a clear, water-impermeable sealer.

2. Process of claim 1 wherein an aqueous solution of magnesium chloride is used having a concentration of at least 14 B.

3. Process of claim 1 wherein an aqueous solution of magnesium chloride is used having a concentration of at least 22 B.

References Cited UNITED STATES PATENTS 1,558,783 10/1925 Bleecker 94-24 1,637,321 7/1927 Johnson 264-338 1,857,511 5/1932 Johnson 9424 2,172,628 9/1939 Treuhaft 9422 X 2,280,333 4/1942 Williams 94-22 2,771,824 11/1956 Patch 94-3 JACOB L. NACKENOFF, Primary Examiner US. Cl. X.R. 94-3; 2643 3 8 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, J 93 Dated December 9, 9 9

Inventor(s) Clark w. Redeker and Ralph G. Schlosser' It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 5 4, "1 4 Be" should read -1 lBe Column 4 line 2, after completely insert -set for 48 hours The surface of the deck was exposed to--.

SIGEIED CLALEB nasa- FEB9 mo (s im Am mniummhmk mun 1:. sum, :12.

Commissioner of Patents Officer 

